2.2.3. Odour (orthonasal) and aroma (retronasal) detection thresholds
method
Odour detection and recognition threshold values (orthonasal)
and the aroma detection threshold (retronasal) for guaiacol in orange
juice were evaluated using the forced-choice ascending concentration
method described by ISO (ISO, 2002). Thus, the Best
Estimate Threshold (BET) for each panellist as well as the group
BET for the whole panel was determined. The BET for each panellist
was calculated as the geometric mean from the highest concentration
that was not recognised as differing from the others and the
lowest concentration that was identified as differing from the
other samples in the test. The panel BET detection values for guaiacol
odour and aroma in orange juice were calculated as the arithmetic
mean of the BET of the 3 replicates for each panellist and for
each individual assessor replication.
Series of five three-alternative forced choice (3-AFC) tests were
presented to the panellists at one time. In each triangle test the
assessor is presented with three samples, one of which is the orange
juice spiked with the guaiacol and the other two being control samples
(with no guaiacol). The assessor is instructed to indicate the
differing sample for each discriminating test although they could
not perceive the difference. Samples within each set were presented
to assessors in random order and panelists were instructed
to smell from left to right. All evaluations were tested in triplicate.
The value for the detection threshold was defined as the level at
which the differing sample is selected correctly by the panel without
being able to describe the medicinal odour or aroma of the guaiacol.
The recognition threshold was defined as the level at which
the differing sample is selected correctly by the panel and they
could correctly describe the medicine odour or aroma of guaiacol.
2.3. Gas chromatography–mass spectrometry
Headspace Solid-Phase Micro Extraction, SPME, gas chromatography–
mass spectrometry (GC–MS) was used to isolate, concentrate
and quantify guaiacol in orange juice using the standard
addition method (Ouyang & Pawliszyn, 2008). Orange juice samples
were fortified with guaiacol from 0.5 to 100 lg/l.
Sampling was accomplished by adding a 10 ml aliquot of the
juice to a 40 ml glass vial fitted with a Teflon lined cap. The vial
headspace was purged with nitrogen before sealing with the cap.
The sample was equilibrated for 10 min in a 40 C water bath. A
SPME fibre (50/30 lm DVD/Carboxen/PDMS on a 2 cm StableFlex
fibre, Supelco Bellefonte, PA) was manually inserted into the vial
and exposed for 30 min, following the headspace sampling
technique developed in a previous orange juice guaiacol study
(Gocmen et al., 2005). To increase the diffusion of volatile
compounds from orange juice into the headspace, the juice was
stirred using a 4 mm magnetic stirring bar. The exposed SPME
was transferred to the GC injector and desorbed for 5 min at
240 C. All analyses were done in triplicate.
Analyses were performed using a Perkin/Elmer Clarus 500
quadrupole mass spectrometer equipped with Turbo Mass soft-
2.2.3 กลิ่น (orthonasal) และกลิ่น (retronasal) ตรวจสอบขีดจำกัดวิธีการกลิ่นการตรวจหาและการรับรู้ขีดจำกัดค่า (orthonasal)และจำกัดตรวจกลิ่น (retronasal) สำหรับ guaiacol ออเร้นจ์น้ำถูกประเมินโดยใช้ความเข้มข้นน้อยเลือกบังคับวิธีอธิบาย โดย ISO (ISO, 2002) ดังนั้น ดีที่สุดประเมินขีดจำกัด (BET) สำหรับ panellist แต่ละกลุ่มใกล้เคียงกับแผงทั้งหมดที่ถูกกำหนด เดิมพันในแต่ละ panellistคำนวณเป็นค่าเฉลี่ยเรขาคณิตจากความเข้มข้นสูงสุดที่ถูกไม่ตราบใดที่แตกต่างกันจากผู้อื่นและความเข้มข้นต่ำสุดที่ระบุเป็นความขัดแย้งจากการตัวอย่างอื่น ๆ ในการทดสอบ ค่าตรวจสอบเดิมพันแผงสำหรับ guaiacolกลิ่นและกลิ่นในน้ำส้มมีคำนวณเป็นแบบเลขคณิตเหมือนกับของเดิมพันที่ 3 สำหรับแต่ละ panellist และแต่ละละ assessor จำลองมีชุดทดสอบทางเลือกบังคับเลือก 3 (3-เอเอฟซี) 5นำเสนอเพื่อการกั้นครั้งเดียว ในการทดสอบแต่ละรูปสามเหลี่ยมassessor ที่นี่ มี 3 ตัวอย่าง ที่มีสีส้มน้ำ spiked guaiacol ที่และอีกสองถูกควบคุมตัวอย่าง(กับไม่ guaiacol) แนะการ assessor เพื่อบ่งชี้การแตกต่างกันตัวอย่างการรับการจำแนกถึงแม้ว่าพวกเขาได้ไม่สังเกตความแตกต่าง มีแสดงตัวอย่างในแต่ละชุดการประเมินในลำดับสุ่มและ panelists ถูกสั่งกลิ่นจากซ้ายไปขวา มีทดสอบประเมินทั้งหมดใน triplicateThe value for the detection threshold was defined as the level atwhich the differing sample is selected correctly by the panel withoutbeing able to describe the medicinal odour or aroma of the guaiacol.The recognition threshold was defined as the level at whichthe differing sample is selected correctly by the panel and theycould correctly describe the medicine odour or aroma of guaiacol.2.3. Gas chromatography–mass spectrometryHeadspace Solid-Phase Micro Extraction, SPME, gas chromatography–mass spectrometry (GC–MS) was used to isolate, concentrateand quantify guaiacol in orange juice using the standardaddition method (Ouyang & Pawliszyn, 2008). Orange juice sampleswere fortified with guaiacol from 0.5 to 100 lg/l.Sampling was accomplished by adding a 10 ml aliquot of thejuice to a 40 ml glass vial fitted with a Teflon lined cap. The vialheadspace was purged with nitrogen before sealing with the cap.The sample was equilibrated for 10 min in a 40 C water bath. ASPME fibre (50/30 lm DVD/Carboxen/PDMS on a 2 cm StableFlexfibre, Supelco Bellefonte, PA) was manually inserted into the vialand exposed for 30 min, following the headspace samplingtechnique developed in a previous orange juice guaiacol study(Gocmen et al., 2005). To increase the diffusion of volatilecompounds from orange juice into the headspace, the juice wasstirred using a 4 mm magnetic stirring bar. The exposed SPMEwas transferred to the GC injector and desorbed for 5 min at240 C. All analyses were done in triplicate.Analyses were performed using a Perkin/Elmer Clarus 500quadrupole mass spectrometer equipped with Turbo Mass soft-
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